A fresh attempt to salvage the Doha round of world trade talks will be mounted in Singapore this weekend after the International Monetary Fund gave warning today that rising protectionist pressures posed a threat to continuing global prosperity.

Pascal Lamy, the director-general of the World Trade Organisation, will tell the annual meeting here of the IMF and the World Bank that failure to restart the talks in the next six months will result in them being put on ice until after the US presidential elections in 2008.

Gordon Brown, the chancellor, and Hilary Benn, the international development secretary, announced today that Britain would seek to breathe new momentum into the talks with a package of aid, worth $750m (£396m) a year by 2010, to help poor countries boost their capacity to trade.

Mr Brown, who chairs the IMF's main policy-making body, said: "Singapore is a critical opportunity for the developed world to show leadership and regain momentum to unblock the stalled trade talks and reach out for the trade deal that offers the world its best hope for long-term prosperity and the only path out of poverty for the developing world.

"But, in addition to providing countries with the access to trade, we must demonstrate our commitment to provide the practical support to reduce their transport and other costs which are, in some countries, a greater barrier than tariffs."

In its half-yearly world economic outlook, released today, the IMF said the failure of the trade talks was deeply disappointing and cast a shadow over the strongest period of sustained growth in the global economy since the early 1970s.

The IMF's economic counsellor, Raghuram Rajan, said: "There could not be a more serious event. Even though financial markets took the collapse of the talks in their stride, for the medium-term health of the global economy there needs to be a continuous improvement on the trade front."

He added: "The collapse of the Doha round, the rising tide of economic nationalism coming in the way of cross-border mergers, the strengthening resistance to immigration - all these are signals pointing in the same direction. In the name of national advantage - an attitude of 'me-my-mine' - politicians are once again ensuring collective disadvantage."

Despite an even stronger performance by the global economy than it had been expecting in the spring, the fund remains concerned about looming threats, including a crash in the US housing market, rising inflationary pressures and an abrupt unwinding of economic imbalances that have left the US with a record trade deficit and China with a huge trade surplus.

The IMF said it now expected growth to be 5.1% in 2006 followed by a 4.9% expansion in 2007 - about a quarter-point higher than it was anticipating in April. "This strong central forecast is surrounded by more uncertainty than usual, with risks tilted to the downside," said Mr Rajan.

The IMF believes that the Federal Reserve, The US central bank, faces a policy dilemma as it grapples with evidence of a slowdown in the housing market at the same time as inflationary pressures are mounting. "The forecasted housing market slowdown is well and truly here, with house price appreciation close to zero," said Mr Rajan. "Indeed, rising inventories of unsold houses suggest things will get worse before they get better."

Against that background, the fund believes that the Fed was right to pause from raising interest rates at its meeting last month, but Mr Rajan said pausing too long carried its own risks. Tight labour markets, rising wages and falling productivity all implied that unit labour costs were increasing.

Should inflationary pressures become entrenched, he added, the Fed would have to raise interest rates even higher and for longer. "The Fed may soon be on the horns of a dilemma, and monetary policy will need to be skilfully managed if the economy is not to be gored."

Elsewhere, the IMF report said there was evidence of expansion gathering pace in the euro area, with growth on course to hit 2.4% this year - the fastest since 2000. The fund warned the European Central Bank, however, against over-aggressive increases in interest rates. Japan was at last emerging from deflation, but the real driving force behind global economic strength had been the leading developing countries of Asia: China and India.

Despite moves by Beijing to slow the economy, the IMF has pencilled in growth of 10% in both 2006 and 2007 for China, while India is forecast to expand by 8.3% in 2006 and 7.3% in 2007.